Downy mildew threatens organic spinach prospects

Downy mildew proliferation could bring organic spinach production to a crisis point in less than three years if steps aren’t taken to fend it off, according to scientists and industry representatives at a Yuma, Ariz., symposium.

“If you don’t come together now on this issue, you will fall as individuals sooner versus later,” Jim Correll, a University of Arkansas plant pathologist, told organic spinach growers and breeders meeting Jan. 8 at Gowan Seed Co.

Bornt Family Farms and the United Vegetable Growers Cooperative organized the event for more than 70 participants. Processors there included Earthbound Farm, Taylor Farms, Dole and Fresh Express.

Until 2003, only four pathogen races were identified. Now there are 14. For the first time producers are seeing multiple downy mildew pathogens in one field, and it’s raising alarm for some.

No known organic fumigant is effective. For now, growers hope that diversifying varieties will stop an entire field from being lost at once.

“The path that the industry is on is just not sustainable,” Eric Schwartz, chief executive officer of Salinas, Calif.-based United Vegetable Growers Cooperative, said after the symposium. “The breeders can’t keep up with the different strains that are popping up.”

“The main objective was to make sure that industry representatives walked out of the meeting on the same page,” Schwartz said. “There has been a spectrum. Some people don’t think it’s an issue, some think it’s a huge issue.

“The answer is somewhere in between. But everyone agreed that the current path is a real problem if it’s not addressed now.”

The issue is specific to organic spinach because sprays and other controls can ward off problems on conventional product.

One scientific hypothesis has been that spores can lie dormant in a field for several years. That hasn’t been verified, but might explain why downy mildew can materialize in a field when it returns to spinach production after a gap of some years.

“Steam treating of seeds has been tried, but what the researchers have learned is that not only are spores airborne, they can be in the soil and do go dormant,” Schwartz said. “That’s what makes it such a challenge. Downy mildew likes cold, wet conditions, and those are spinach growing conditions,”

“The industry is starting to see the yields be impacted,” he said.

One concern producers have is whether there is sufficient diversity in spinach seed production. Most seed is grown in Denmark — about 16,000 acres versus less than 2,500 in the Pacific Northwest.

The California Leafy Greens Research Board and California Seed Association plan to spotlight the issues in the coming months, Schwartz said.